1. Field of the Invention
The present invention relates to a reciprocating compressor, and particularly, to a stator fixing apparatus of a reciprocating compressor and a fabrication method thereof capable of preventing deformation of an original shape or increase of a defect rate due to a molding material by omitting an over-molding process using the molding material in a stator fabricating process, and of improving efficiency and reliability of the reciprocating compressor by facilitating discharging of heat and moisture.
2. Description of the Conventional Art
In general, compressors convert electrical energy into kinetic energy and compress a refrigerant gas by the kinetic energy. The compressors, as a main component making up a refrigeration cycle system, include various types such as a rotary compressor, a scroll compressor, a reciprocating compressor and the like according to a compression mechanism. The refrigeration cycle system including such compressors are used in refrigerators, air-conditioners, showcase coolers and the like.
The reciprocating compressor among those compressors is a compressor in which a piston linearly reciprocates in a cylinder, and sucks and compresses gas for discharging it, an example of which will be shown as follows.
FIG. 1 is a sectional view showing an example of the conventional reciprocating compressor, FIG. 2 is an exploded perspective view showing an outer stator fixing apparatus of the conventional reciprocating compressor, and FIG. 3 is a front sectional view showing a fixed state of the outer stator in the conventional reciprocating compressor.
As shown in those drawings, the conventional reciprocating compressor includes: a frame unit 20 elastically supported in a casing 10; a reciprocating motor 30 supported by the frame unit 20, and having a mover 33 which linearly reciprocates; a compression unit 40 connected to the reciprocating motor 30 and supported by the frame unit 20; and a resonant spring unit 50 for elastically supporting the reciprocating motor 30 and inducing its resonant motion.
The frame unit 20 includes: a front frame 21 for supporting a front side of the reciprocating motor 30, a middle frame 22 coupled to the front frame 21, for supporting a rear side of the reciprocating motor 30; and a rear frame 23 coupled to the middle frame 22, for supporting the resonant spring unit 50.
The reciprocating motor 30 includes: an outer stator 31 having a coil winding and fixed to the front frame 21; an inner stator 32 positioned inside the outer stator 31 spaced therefrom by a certain air gap and fixedly inserted into a cylinder 41; a mover 33 interposed in the air gap between the outer stator 31 and the inner stator 32, for linearly reciprocating.
The outer stator 31 includes a bobbin body 31a in which the coil bonding is inserted; several core blocks 31b are formed by laminating a plurality of stator core sheets in a circular arc shape, and inserted in both sides of the bobbin body 31a to be coupled thereto; a molding body 31c fixed to the bobbin body 31a by molding a connected portion of each core block 31b. 
The molding body 31c is formed of an insulator such as epoxy so as to consecutively fix an outer circumferential surface of the bobbin body 31a and the connected portion of each core block 31b. 
The compression unit 40 includes: a cylinder 41 fixed to the front frame 21; a piston 42 slidably inserted in the cylinder 41 and coupled to the mover 33 of the reciprocating motor 30, for reciprocating in upper and lower directions; a suction valve 43 mounted on a front end surface of the piston 42, for opening/closing a suction path F; a discharge valve 44 mounted in an outlet of the cylinder 41, for restricting the discharge of a compressed gas; a valve spring 45 for elastically supporting the discharge valve 44; a discharge cover 46 having the discharge valve 44 and the valve spring 45 therein and covering the outlet of the cylinder 41.
The resonant spring unit 50 includes: a spring support 51 coupled to a portion connected between the mover 33 and the piston 42; and a first resonant spring 52 and a second resonant spring 53 provided at upper and lower sides of the spring support 51 and formed of a compressed coil spring to elastically support the piston 42.
Among previously unexplained reference symbols, M denotes a magnet, P denotes a compression space, SP denotes a suction pipe, and DP denotes a discharge pipe.
An operation of such conventional reciprocating compressor and a structure thereof will now be explained.
When power is applied to the outer stator 31 of the reciprocating motor 30, a flux is formed between the outer stator 31 and the inner stator 32, and thus the mover 33 and the piston 42 move along the direction of the flux. A this time, the mover 33 linearly reciprocates by the resonant spring unit 50 and the piston 42 also linearly reciprocates in the cylinder 41, whereby a pressure difference occurs in the compression space P of the cylinder 41. As a result, a series of processes, namely, sucking a refrigerant gas, compressing the refrigerant gas until it has a certain pressure, and discharging it, are repeatedly performed.
Here, in order to assemble the reciprocating compressor, as shown in FIG. 2, the core block 31b is formed by perforating a plurality of stator core sheets as a thin plate and laminating them. Afterwards, this core block 31b is inserted in an outer side surface of the bobbin body 31a having the coil winding in a particular mold, and then the molding body 31c is formed by performing an overmolding between a connected portion, between the outer circumferential surface of the bobbin body 31a and the core block 31b, and a space, between the outer circumferential surface of the bobbin body 31a and an inner circumferential surface of the core block 31b, thereby resulting in forming the outer stator 31. Thereafter, the outer stator 31 is separated from the mold. The outer stator 31 positions between the front frame 21 and the middle frame 22 together with the inner stator 32 and then is fixedly coupled to the frame unit 20 by using a coupling bolt 24 and a coupling nut 25.
However, in the conventional reciprocating compressor, a molding pressure generated when a molding material is injected during the process for fabricating the outer stator 31 of the reciprocating motor 30 or a contracting force generated when the molding material is hardened pressurize the core block 31b, which may cause deformation of parts of the core block 31b. As a result, a distance between cores positioned between the outer stator 31 and the inner stator 32 is narrower, and accordingly an appropriate air gap between the outer stator 31 and the inner stator 32 is not maintained, thereby causing degradation of efficiency and reliability of the compressor.
Moreover, at the time of an initial injection of the outer stator 31, an initial loss may occur when conditions of temperature and pressure for the molding material are established, and a defect rate may be increased due to the ununiformity of the product according to the injection molding temperature.
In addition, in case of the overmolding structure at the time of assembling the outer stator 31 by injection, as shown in FIG. 3, the outer stator 31 is formed in a hemi-sealed shape, which may make it difficult to discharge heat and moisture from the coil winding and thus lower a motor efficiency.